Pumps. Pumping equipment

ENCE Engineering LLC, Moscow, Russia, being an engineering and service center of the company ENCE GmbH / Switzerland supplies production machinery for oil and gas and chemical industries and specializes in the delivery of hi-tech special customized pumps strictly according to the Customers’ requirements and specifications. The company employs erection supervision and commissioning specialists for installation of a wide range of pumping equipment and systems.

Pump is a mechanical device for transferring fluid from lower to upper point or from low-pressure zone to high-pressure zone.

“Fluid” means any liquid or gas. Pumps can be classified into variety of types depending on their application, specifications, medium, design, etc.

Pumping equipment can greatly differ by design, as well as by operation principle and application, there are, however, several governing parameters, which are common for all of them. These are flow rate, head, power, and efficiency coefficient.

1) Flow rate is determined by fluid volume, which can be transferred by pump within unit of time. The unit of measurement is m3/sec.

2) Head is a value, which represents quantity of energy delivered by pump to transferred fluid mass unit. The unit of measurement is meter.

3) Power is generally subdivided into consumed and useful. Useful power is directly spent for media transferring. Consumed power stands for power, which is delivered by motor to pump. The unit of measurement is Watt.

4) Efficiency coefficient establishes relationship between consumed and useful power and characterizes effectiveness of pumping equipment operation. More advanced construction of pump provides for less power losses, and this leads to higher efficiency coefficient.

Besides main characteristics, it is possible to highlight several secondary qualities, which would determine applicability of particular pump for given specific area. This can be noise level during operation, flow path resistance to corrosion, type of hermetic sealing, service life, availability or absence of self-priming function etc.

1. International manufacturers of pumps and pumping equipment for chemical and oil industries

Sundyne International S.A.(USA) – has been a manufacturing plant of centrifugal single-stage high-speed pumps since 1957.

Shin Nippon Machinery (Japan) – has manufactured and developed centrifugal single and multi-stage pumps since 1951.

Teikoku Electric (Japan) – has manufactured and developed centrifugal canned pumps since 1939.

Oilgear (USA) – has manufactured and developed high pressure and high-high pressure piston pumps and pump systems since 1921.

2.3. According to purpose and transferred media

3. Supplied pumps

Positive displacement pumps

Pumps as a hydraulic machine can be of rotodynamic and positive displacement type. A positive displacement pumps operate by sequential filling of the working cavity by transferred media and subsequent displacement of this media. Additional energy is transferred to fluid in rotodynamic pumps by moving working parts of such pump. This is one of the fundamental classifications, since it is based on main principle of pumps operation. Therefore, in spite of large variety, pumps of the same type would have similar particularities, which are displayed to a greater or lesser extent according to specific implementation of operation principle.

Piston (plunger) pump – pumping equipment of positive displacement operation. Operating device consists of fixed working cavity, which is cylinder with two valves where moving part (plunger or piston) travels back and forth. Plunger can be actuated by crank mechanism or manually by lever.

When the piston moves back, volume of working cavity increases and pressure decreases, which provides for suctioning of transferred media. Meanwhile in order to prevent fluid backflow the input channel valve is open and the output one is closed. When working camber is filled, the piston starts moving forward. At that, valves are switched and transferred media is displaced into output channel. Fluid constantly moves while operating cycle is repeated.

Described principle of operation provides plunger and piston pumps with several distinctive features, which determine areas of their application. First, it is discontinuity of delivery in same-volume portions and this makes such type of pumps hardly applicable in cases when uniform feed is necessary, but these pumps are successfully applied in internal combustion engines and other areas, where feeding in portions is required. Second, self-priming is an ability to start pump without preliminary priming. Third and the most important factor is that piston and plunger pumps are able to generate extremely high pressures on output, meanwhile maintaining relatively small flow rate. Because of these factors, such type of pumps is widely applied in water-jet units, which are used for surface cleaning by guided high-pressure jet of fluid.

Diagram of piston (plunger) pump operation principle

Diaphragm pump – design principle of working cavity of this type of pumping equipment is similar to piston pump and the only difference is that instead plunger or piston there is flexible membrane installed, which is actuated mechanically or pneumatically.

Implementation of membrane provides several advantages over piston pumps and defines specific nature of their application. One of the main features – absence of sealing in pump construction and this allows for usage of diaphragm pumps for operations with mediums, whose leakage is not allowable. These mediums can be toxic, highly volatile or explosive. Diaphragm pumps can also easily transfer fluids with solid inclusions. Lubrication of moving parts is also not necessary and this simplifies servicing and operation. However, in relation to piston pumps, decreased produced pressure and increased wear of working membrane are main disadvantages of diaphragm pumps.

Diagram of diaphragm pump operation principle

Screw pump – pumping equipment of positive displacement action, where working cavities are created by restricting space between pump body and rotating part – screw (conical screw is used in this case) or several screws. While screws are rotating, confined space with transferred medium in it moves from input nozzle to output nozzle and media is transferred by this action.

Screw pump is self-primed, just as any other positive displacement pumps. They differ from most of other positive displacement pumps by almost absent feed non-consistency. Because of structural features these screws pumps are low-noise in operation, able to develop substantial head and transfer mediums with solid inclusions without breaking these inclusions. Combination of screw pump’s features allow for their successful application in several areas, such as food, chemical, petrochemical etc. Production of these pumps is expensive and involves many technical problems, but in most cases, their effectiveness outweighs these disadvantages.

Diagram of screw pump operation principle

Rotary-vane pump – hydraulic machine of positive displacement action, which creates several working chambers during operation by separating space by pump body, rotor and two nearby plates (vanes). The rotor is located inside of body and has slots, where plates are freely installed (or under force of spring). One end of these plates is resting and sliding against body. Rotor and body axis are offset, therefore volume of given working cavity changes during rotor rotation and fluid is transferred because of this action.

Rotary-vane pumps are not widely used comparing to piston or centrifugal ones, but they have several advantages that can make their application more advantageous. Pumps of this type are compact, do not have significant feed inconsistency and they are fairly simple to manufacture and operate. Construction of operating device provides possibility to operate in reverse mode and if fluid is forced into the pump, it can operate as a hydraulic motor. Plates are wearing the most, but they are easy to replace and this simplifies repair and servicing.

Additional emphasis can be placed on water-packed pumps. Plates are rigidly fixed in such pump. Sustainable ring of fluid is created inside of body during operation and rotor, plates, body and surface of fluid ring create the working cavity. Pumps of this type are used as vacuum pumps. Absence of contacting parts is obvious advantage of these pumps and this provides the pumps with high resistance to various impurities. Some disadvantages of water-packed pumps lie in necessity to add system for fluid catching and returning, which is carried-over with transferred gas during operation.

Diagram of rotary-vane pump operation principle

Gear pump – pumping equipment with meshed gears. Gears are placed into body and working cavities are created between body walls and nearby gear teeth. When teeth of nearby gears are meshed, it leads to decrease of corresponding working cavities volume. This in turn leads to displacement of transferred medium portion into discharge nozzle.

Pumps of this type are able to operate in reverse mode; their construction is simple and can reach high speeds of gears rotation. At that, their reliability factor is higher than in many pumps, which are used for similar purposes. Gear pumps are frequently applied for transferring of various viscous mediums, such as molten polymers or liquid building mixes. Meanwhile operation principle of the gear pump requires increased accuracy of parts manufacturing in order to exclude possibility of transferred medium backflow during operation.

Diagram of gear pump operation principle

Peristaltic (hose) pump – pumping equipment of positive displacement action with simple construction, but unusual operation principle. Flexible tube or hose is the operating device of the peristaltic pump. This hose envelops the rotor with rollers on it. Hose can be pressed against rollers by tension force or roll against special surface. Hose is completely pinched while interacting with roller and part of its volume is separated by this action. While rotor rotates, these separated volumes are moving inside of hose until getting into discharge section of hose.

This type of construction provides several advantages over most of other pumps and this makes peristaltic pumps irreplaceable in some cases. Main feature of these pumps is that there is no metal-metal contact during operation and this greatly extends service life of its moving parts (except for hose) and there is no contact between medium and pump parts. Latter feature has led to wide usage of peristaltic pumps in medicine and pharmaceutics, where it is necessary to transfer medium without deformation and contamination, as is in case of blood forced circulation. Only flexible element (tube or hose) is susceptible to wear and this element is easily replaceable, which simplifies servicing and repairing. This type of pumps is also self-primed. At the same time maximum developed pressure of peristaltic pumps is low, flexible element is susceptible to high wear and its maximum operating temperature is limited.

Centrifugal pump – one of the most widely known and used type of pumps. Additional energy is delivered to pumped fluid by centrifugal force, which acts upon transferred medium from blades that are rigidly fixed on working wheel in pump body. Impeller is rigidly fastened to shaft, which is driven by the engine. Compared to most of positive displacement pumps, the centrifugal pumps are not self-primed and before starting, they require preliminary priming with fluid.

This type of pumps is not able to operate with large fluid flow rates, at that fluid is delivered continuously without discreteness, which is inherent for positive displacement pumps. Centrifugal pumps production involves some difficulties, but operation and servicing of these pumps is fairly simple. In case of working impeller malfunction, it is easy to dismantle from working shaft and replace by new one. Absence of any valves in construction of centrifugal pumps also contributes to its reliability and resistance to any inclusions in transferred medium. Axial force unavoidably appears during the pump operation. Several engineering solutions are implemented for compensation of such force, such as installation of second impeller onto shaft to cancel out axial forces. It is possible to increase head of the centrifugal pump by sequential installation of several impellers on single shaft and providing multi-stage construction.

Diagram of centrifugal pump operation principle

Axial pump – impeller placed in cylindrical body. When the impeller rotates, pressure differential is created on its opposing sides and fluid is transferred by this action. Axial pump requires priming before starting, just like the centrifugal one.

Axial pumps provide lesser head in comparison to similar centrifugal pumps, but their extreme simplicity of construction and possibility to install the pump immediately into line make them particularly preferable in some cases.

Diagram of axial pump operation principle

Vortex pump – hydraulic machine of rotodynamic action. The operating device is impeller with radial or inclined blades. The impeller is installed inside of body with minimal gap. Impeller and body create free annular space. When impeller rotates, incoming water flow is whirled by blades and vortexes are created by this action. Meanwhile blades accelerate fluid several times while it flows through annular cavity of pump.

Usually vortex pumps are compared to centrifugal pumps, since they have many common features and can be used for similar purposes. Because of fluid motion pattern inside of body, this type of pumps creates higher head comparing to similar centrifugal pump. Therefore, it is used, when it is necessary to feed fluid with relatively low flow rate, but with high head. It is also should be noted that vortex pump is reversible, i.e. it can operate in forward and reverse directions, and is self-primed in comparison to centrifugal pumps. These features allow using vortex pumps for transferring of gas-air mixtures and liquefied gases. Decreased efficiency coefficient is disadvantage of vortex pump.

Disk pump – hydraulic machine of rotodynamic action, where medium is transferred without impacts. Construction of these pumps is similar to centrifugal pumps, but construction of impeller differs greatly. Operating device of the disk pump consists of closely fit disks on single shaft and these disks have no blades. Transferred fluid moves from center of disks to their periphery and this movement is promoted by laminar flow of fluid layers near disks, which draw away intermediate layers.

Transfer of medium without impacts provide disk pumps with several significant advantages, which define area of their applicability. Low noise of such pumps is of great importance, as well as delicate handling of working medium, when pump has almost no effect on medium. Additional advantage in this case is low reverse influence; therefore, it is advisable to use disk pumps for abrasive medium pumping. Ability to operate under extremely high rotational speed of working shaft is also important, since this feature provides for high cavitation qualities of disk pumps. All stated advantages, including simplicity of construction and manufacturing, justify usage of these pumps in many cases in spite of relatively low efficiency coefficient.

Diagram of disk pump operation principle

Worm pump – consists of two main elements. One of them is rotor, which is referred to as the worm, and the other is stator, which is the pump body. The worm is manufactured out of corrosion and abrasion resistant metals, the stator has inner lining made of several types of elastomers. When the rotor rotates, it catches, then separates while coming into contact with the stator and pushes trough portions of transferred medium. Combination of all transferred portions forms the flow of media trough the pump.

Because of worm pumps’ construction, which does not create impact forces for transferred material, they are applied for transferring of fluids, which according to operation process shall not be damaged during transportation in pipeline. This type of pumps is successfully used for transferring of thick and viscous mediums; therefore, this pump is widely applied in food, chemical and petrochemical industries.

Application of pumping equipment

Depending on specific task, the pumping equipment of different design and operating principle can be applied in the same area. Here we will discuss come of pumps’ groups, which are associated by their purpose.

Metering pump – pumping equipment intended for dosing preset quantities of fluid. Positive displacement pumps are ideal for this purpose: piston, membrane etc. They allow for metering of preset quantity of transferred medium and prevent backflow of fluid. In order to execute such function these pumps might be provided with additional systems or have some design particularities. Piston pumps can be equipped with several working cavities, which are actuated from single drive and have offset operating cycle relative to each other. Some models are additionally equipped with mechanism for adjusting the cavity working volume in order to provide more accurate dosing. For control and dosing, the pumps of this type are equipped with stepper motors or other control devices, so the operating device would execute preset quantity of movements. Particularities of implemented type of pump are also considered for dosing purposes. For example, membrane pumps are used, when metered fluid is poisonous, chemically aggressive or explosive.

Slurry pump – pumping equipment, which is intended for withdrawal of fluids with high content of solids of various sizes. It can be bottom sediment from various reservoirs, tanks and foundation pits, river sand and slurries. Slurry pumps can be of regular submerged or semi-submerged construction. Centrifugal pumps are usually implemented for these purposes. Meanwhile additional requirements are applied for them: resistance to abrasive wear and ability to transfer medium with high content of solids. These features are provided by usage of wear-resistant materials and selection of optimal relation between impeller rotation speed and impeller size, since if rotation speed lowers, abrasive wear of its elements increases and size increases accordingly.

Booster pump – functions as a component part of pumps units and intended for pressure increasing or providing additional vacuum in system. Has design of vacuum pump (can be of oil-vapor, steam-jet, mechanical etc.). It is used in water supply system for increase of head. Booster pump can be installed before main operating pump in order to provide operation of latter in mode without cavitation or to provide intake of fluids from remote vessels.

Mud pump – single-purpose type of pumping equipment, which is implemented in drilling equipment and intended for providing mud fluid circulation in drilled well. Construction of such pump can be of rotodynamic or positive displacement type. Axial, plunger and piston types of pumps are used. Such severe operation conditions are reason for several requirements for mud pumps. They must provide constant and uniform feed of mud fluid in order to prevent unwanted influence of pulsations. Meanwhile they should be powerful enough to circulate fluid and be resistant to abrasive wear by circulated fluid and should provide for possibility to quickly repair and replace broken parts.

Deep-well pump – pumping equipment mostly of semi-submerged design, when below level of pumped fluid there is only operating device – impeller. These pumps have long cylindrical body, which simplifies installation into operating position. Deep-well pumps are able to create high head, enough not only for fluid lifting, but for its feeding trough pipeline as well.

As the name implies, the deep-well pump is applied for fluid lifting out of various wells and pits. They can be used for water supply from artesian beds and for pumping water out of flooded basements and trenches. Submerged pumps can be also used in mining, chemical, construction and other industries.

Foam pump – pumping equipment, which is intended for transferring of emulsions and pulps with various coefficient of phases. Vertical foam pump is construction combined in one device and consists of engine, dedicated reservoir and centrifugal pump. Distinguishing feature of foam pumps is conical reservoir with tangential emulsion intake. Rotating impeller creates vortex cavity of transferred medium in this intake, where gas part is separated and liquid part falls onto working impeller and discharged into nozzle.

Main feature of this type of pumps prescribes its area of application. Foam pumps are used in any facilities, where it is necessary to transfer various types of emulsions. Such pumps are used in waste treatment facilities, where it is necessary to remove floating layer in floatation facilities and in enrichment plants, oil-producing and oil-refining facilities. Foam pumps are also used for construction, since they are able to pump construction mixes.

Fire pump – basically it is console centrifugal pump, which is outfitted for firefighting purposes. Since centrifugal pump does not have self-priming ability, it can be connected to vacuum pump for priming if water is drawn from water body. If firefighting fluid is drawn from tank, which is located above level of suction nozzle, then priming is not necessary. Fire pump can be additionally equipped with pressure gage and system for head dynamic change in order to prevent damage to pump or firefighting hose in case latter was quenched or clogged. If foam mixture is used for firefighting, then fire pump will be equipped with foam mixer for foaming, where pumped water is mixed according to preset proportion with foam-producing agent, which is delivered from separate vessel.

Bucket elevator. History of pumping equipment

Pump is a hydraulic machine, which is intended for transferring of liquid mediums. This simple definition is backed by centuries of pumping equipment development from simplest mechanisms (such as Archimedean screw and lever pump) to modern pumps, which are able to provide extremely high head and having incomparable higher efficiency coefficient.

Mechanisms, which are able to transfer fluid, became necessary when demand for fluid had risen in areas, to which fluid was not able to get by gravity, and has surpassed possibilities to transfer fluid manually in vessels (buckets, barrels etc.). In ancient times, areas suitable for human settlements besides other factors were defined by availability of water resources. For that reason large settlements existed only near large rivers, various water bodies and wells, which were able to fulfill demand for fresh water. Growth of settlements and agricultural development encouraged construction of canal systems, but water continued to move under influence of gravity. However, bucket elevator was invented in ancient Egypt. It was undershoot water wheel, which was simple bucket elevator able to lift fluid up to certain height. It allowed to fill with water reservoirs, which were above canal level and to create additional head. Although the bucket elevator is not a pump, it represented future vector of pumping equipment development. View on pumps as simple mechanisms for fluid transferring had to be redefined much later, when sophisticated machines were invented and developed.

Today, pumping equipment besides simple fluid transferring has to meter fluid, transfer large volumes of fluid or feed under high pressure, and has to be able to operate with viscous, explosive or chemically active mediums. Improvement of pumping equipment would be impossible without development of exact sciences, creation of new materials (various alloys, polymer membranes etc.), and nowadays without development of electronic devices for monitoring and control.